You are going to want to start with your GP who will then give you a reference to an ENT. The ENT will handle your primary care for this at that point and will do what needs to be done to get a firm diagnosis of what's going on. The ENT will get a biopsy done of this mass and then order pathology testing which will tell you for certain if the mass is or is not cancer. If it IS cancer, then the ENT will will work with you to get a referral to a cancer center where they will then establish a treatment plan for you.

I would say this is a pretty typical process that most people here went through. The important thing is to get the ball rolling. See your GP as soon as possible and they will get you the referral you need. And don't panic. You don't KNOW you have cancer yet. It could be a lot of things other than cancer. Like many many things.